Radio signaling system



Jan. 7, 1930. I s, LQEWE 1,742,773

RADIO SIGNALING SYSTEM Filed Jan. 5, 1928 INVENTOR S\E MUND LOEWE A ORNEY mum nonwqa, or BERLIN, enmity, assrenoa AMERICA, 4" conronaf'rrou' or nmwnu:

mro sternum iszsrnu- Application fled January 5, 1988, Serial Io. 244,626, 'and in Germany December 18, 1920; I

An application for atent for this invention has been filed in ermanyon December This invention relates to a radio signaling system and especially to an improved radio I receiving circuit.

Eflicient receiver apparatus is required to combine high selectivity, high sensitiveness and simplicity in operation and manipula.

tion. A number of receiver principles are in actual use which more or less measure up to these requirements. While it is comparatively easy to insure high sensitivity in receiver apparatus, the requirement of insuring simultaneous high selectivity and simplicity in operation and construction militate against each other in so far as high selectivity according to the present state of the art is concerned. At present high selectivity may be obtained only by the provision of a number of filter circuits which are tuned either to the incoming wave or to intermediate frequencies produced by the superposition of locally produced waves. But the selective action, on the other hand, should not be pushed to a point where the passed frequency band becomes un-' duly narrow, for inv such case the characteristic overtones of the transmitted speech or music are eliminated, and this results in-a so greatly impaired quality of reproduction.

The object of this invention is to provide a radio receiving system having extremely high selectivity and yet allowing of audio reproduction of high quality. This I accomplish by utilizing a piezo-electric or stal and intermediate frequency energy of a' requency hi her than the'incoming wave so that the side bands utilized will vary but a few percent from the intermediate frequency and thereb 40 not be eliminated by the use of the crystall Fundamentally speakingQthe well-known quartz crystal resonators would be highly suited for the puipose of increasing the selective action 0 eceiver apparatus, but the damping of the same'is so low that the inof the working wave,

below 200 meters are used, while it excellent for waves less than 150 meters.

convenience of side band elimination would arlse in as much as the resultant frequency band that is passed by the crystal isunduly narrow for good reproduction.

However, this disadvantage will play a much less serious part, the shorter the length contradistinct from what holds good for operation 011 waves of, say, 1000 meters in length where serious impairment-of speech transmission will arise. If selection is eifected by means of'a quartz crystal-resonator tuned to 1000 meters good reproduction is had as soon as wave-lengths becomes ThlS is due to the naturaldampmg condltlons of quartz crystals, and to the fact that, the lighter the frequency, or, in other words, the less the length of the wave, the smaller (expressed in terms of percent) will be the'frequency change caused by the superposed speech or music. This fact is utilizedaccording to the disclosures of the pres'entiinvention in the followingway. 131, 2

While in known transposition arrange- .ments, it is usually the difierential frequency between the incoming and the local waves that is used as the intermediate frequency (a frequency that is far lower than either of the two components), it is the integrated frequency which is employed according to my invention. This integral frequency is substantially higher than that of its components. Under usual conditions the integral frequency corresponds to a wave-length below 150 meters. Hence, this is a very fruitful field of'application for a combination of only moderately selective circuit arrangements and uartz crystals, for it is then possible to uti ize the extremely high selection prop s5 erties of quartz crystals without losing the amplification of the side-band frequencies. While the quartz crystal is depended upon for selection, the remainder of the apparatus may be made moderately selective, in other To mm 'oonronurlon or words, resistance-coupled radio frequency, integral frequency and audio frequency amplifiers may be employed, preferably in the shape of the known resistance-capacity-coupled multiple-unit tubes.

A circuit arrangement embodying the fundamental idea of my invention hereinbefore outlined is shown by way of example in the accompan ing drawing. The incoming energy, pick up b the loop antenna 1 comprisin tuning con enser 2, is fed to the tube 3. 4 denotes the local oscillator or heterodyne. The circuit 5 is tuned to the integrated frequency; transfer of energy to the subsequent integrated frequency and audio fregllliency systems is effected by the agency of e quartz resonator 6 which is likewise tuned to the integral frequency. The said resonator acts with regard to all frequencies deviating from its natural period like an extremely high capacitive impedance while its impedance is extremely low for the resonance frequency of the quartz crystal. Hence, the energy transfer to the subsequent amplifier sta es is effective substantially only for the sai I frequency, the said subsequent stages being indicated at 7 and 8 representing resistance-capacity-coupled tubes. To prevent charging of the grid of tube 7, the grid may be provided with resistance 9 to afford a leak to the cathode or to a potentiometer for the plglrpose of suitable selection of biasing potenti I claim as my invention :1

1. In a receiver circuit, an antenna for collecting radiated energy, an electronic discharge device, said antenna being coupled to the input of said device, means for impressing locally generated high frequency oscillations on the out ut circuit of said device, amplifier and rectifier means, a resonant circuit in said output circuit tuned to the inte ted frequency made up of incoming and ocally generated oscillations, and a coupling means between the resonant circuit and said amplifier and rectifier means comprising a piezo-electric means havin a resonant frequency equal to that of sai integrated frequencg.

2. heterodyne receiver circuit comprising an electronic discharge device having an input and output circuit, an antenna coupled to said input circuit, a source of local oscillations coupled to said output circuit, aresonant circuit tuned to the integrated frequency of the incoming and locally generated waves in said output circuit with said last mentioned coupling means, .an amplifier tube, and a piezo-electric crystal couplin said resonant circuit and said amplifier tu%e,said crystal having a natural period of vibration equal to said integrated frequency.

3. For a receiver circmt, means for collecting desired signal energy, frequenc changing means, including an electron (fischarge sum frequency.

SIEGMUND LOEWE. 

